1. Field of the Invention
The present invention relates to a keeper for dental magnetic attachments so as to fix a denture base by magnetic attraction, and a method for removing the body of the keeper from the tooth root.
2. Discussion of the Background
Dental magnetic attachments to fix denture by magnetic attraction are being developed in the dental field. A known dental magnetic attachment 9 is as shown in FIG. 8. It is composed of a magnetic assembly 91 and a keeper 92 embedded in a root cap 82 to be attracted by said magnetic assembly 91. A magnetic attractive force is generated between said keeper 92 and said magnetic assembly 91. A dental magnetic attachment having the structure mentioned above requires that keeper 92 is incorporated into the root cap 82 by a casting method.
This process in which the keeper 92 is incorporated into the root cap 82 requires precise control of casting conditions at an elevated temperature to maintain the good quality of the keeper 92. This casting process requires a lot of time and is apt to cause various problems. As a result the cost of keeper preparation is increased significantly. It also prolongs the period for medical treatment to the patients.
Therefore, at the present time, the keeper is cemented directly on the root surface with the application of advanced dental resin. In this case, the keeper 92, consisting of a body of keeper 921 and a post 922, is fabricated by machining, as shown in FIG. 9 and FIG. 10.
However the keeper 92 mentioned above faces following difficulties. First, as seen in FIG. 9 and FIG. 10, said post 922 has rather large diameter because of the limitation of machining capability. The thick post requires enlargement of the tooth canal, which makes the root fragile. Furthermore, the shape of said post 922 has no resistance against the post becoming dislodged from the root canal. Second, in the situation where the root surface is inclined against root canal, while the root cap in which a keeper is incorporated by casting can be fitted to such surface inclination, a keeper with the post 922 made by machining can not be adjusted to the inclination. Third, said keeper 92 requires a great deal of time to be removed in case of diagnosing by MRI (magnetic resonance imaging).
The keeper 92 is made of soft magnetic materials, and the material causes an undesirable influence on an MRI image. In the case where patients need to get an MRI diagnosis, both the body 921 and post 922 should be removed from the tooth root to avoid having an adverse influence on MRI image. Thus, removing of the body and post requires a great deal of time and labor.
Considering these difficulties, the present invention provides a keeper for the dental magnetic attachment which is superior in fitting to the tooth root shape, as well as being easier to be removed from tooth root when necessary. The present invention also offers the method to remove the keeper from the tooth root.